The human eye in its simplest terms functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea, and further focusing the image by way of the lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape and length of the eye, and the shape and transparency of the cornea and lens.
When trauma, age or disease cause the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. The typical treatment for this condition is surgical removal of the lens and implantation of an artificial intraocular lens or IOL.
While early IOLs were made from hard plastic, such as polymethylmethacrylate (PMMA), soft, foldable IOLs made from silicone, soft acrylics and hydrogels have become increasingly popular because of the ability to fold or roll these soft lenses and insert them through a smaller incision. Several methods of rolling or folding the lenses are used. One popular method is an injector cartridge that folds the lenses and provides a relatively small diameter lumen through which the lens may be pushed into the eye, usually by a soft tip plunger. A commonly used injector cartridge design is illustrated in U.S. Pat. No. 4,681,102 (Bartell), the entire contents of which is incorporated herein by reference, and includes a split, longitudinally hinged cartridge. Similar designs are illustrated in U.S. Pat. Nos. 5,494,484 and 5,499,987 (Feingold) and 5,616,148 and 5,620,450 (Eagles, et al.), the entire contents of which are incorporated herein by reference. Several hinge-less cartridges are known. See, for example, U.S. Pat. No. 5,275,604 (Rheinish, et al.) and 5,653,715 (Reich, et al.), the entire contents of which are incorporated herein by reference.
These prior art cartridges all have relatively rigid walls surrounding a smooth, round or elliptical bore that is symmetric about the longitudinal axis. The rigid walls work to fold and compress the IOL prior to insertion. Depending on the IOL material used, friction between the rigid walls and the IOL can make it difficult or impossible to express the IOL from the cartridge without damage to the IOL or delicate ocular tissue. To reduce friction, a common practice is to apply a viscoelastic agent or other biocompatible lubricant to the IOL and/or bore of the cartridge. While the application of a lubricating viscoelastic agent works well with some silicone and hydrogel materials, other materials such as soft acrylics can be very hydrophobic, making it difficult to lubricate these lenses with conventional water-based viscoelastic solutions.
Another limitation of commercially available prior art lens cartridges is that they are all packaged separately from the IOL, requiring the surgeon or operating room staff to load the IOL into the cartridge thereby introducing the opportunity for mishandling or damage to the IOL.
Accordingly, a need continues to exist for an improved IOL injection system that facilitates the loading and expression of soft lenses.